While filming water therapy scenes for her new movie "Cake," Jennifer Aniston was forced to overcome a longtime fear of going underwater.

"I was a kid and I was riding this tricycle around a swimming pool and I drove my tricycle into the swimming pool and I didn't let go and my brother tried to [help me]," Aniston revealed before a recent film screening. "So, I can't go underwater and no one will believe me. I honestly can't."

The actress also has a fear of flying, once reportedly explaining: "I had one really bad flight where we were caught in an electrical storm. It was from Toronto to New York, which is an hour flight and it took two hours. We shouldn't have been in the air. We were flying and every once in a while I'd see a field and I'd say, 'Just land it, put it down, put it on the freeway.'" —XFINITY Entertainment Staff (Photo by: Jason Merritt/Getty)

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He's one of the biggest stars in the world, and has attended countless movie premieres and award shows, but Harrison Ford is deathly afraid... of public speaking?

"The greatest fear in my life is public speaking," Ford said while accepting the AFI Lifetime Achievement Award in 2000. He was also quoted by the AP has having said, "It's people I'm scared of." —XFINITY Entertainment Staff (Photo by: Frazer Harrison/Getty)

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No, Billy Bob isn't scared that Angelina Jolie is going to try and take a vial of his blood again…but he definitely has one of the weirdest celebrity phobias. The actor suffers from obsessive-compulsive disorder, resulting in a fear of everything from antique furniture to certain types of silverware.

"It's just that I won't use real silver. You know, like the big, old, heavy-ass forks and knives, I can't do that," he told The Independent newspaper in 2004. "It's the same thing as the antique furniture. I just don't like old stuff. I'm creeped out by it, and I have no explanation why...I don't have a phobia about American antiques. It's mostly French—you know, like the big, old, gold-carved chairs with the velvet cushions. The Louis XIV type. That's what creeps me out. I can spot the imitation antiques a mile off. They have a different vibe. Not as much dust." —XFINITY Entertainment Staff (Photo by: Jason Merritt/Getty)

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Sarah Michelle Gellar has a huge fear of cemeteries, which leads one to ask: How did she play Buffy the vampire slayer for all those years? They're all dead!

"When I was younger, I used to totally fear that a kidnapper was going to climb up to my twelfth story window - using suction cups like Spider Man - and kidnap me," Gellar told Phase 9 TV. "And I have an irrational fear of cemeteries and being buried alive." —XFINITY Entertainment Staff (Photo by: Frederick M. Brown/Getty)

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Depp spoke with Interview magazine about his attempt to get over his paralyzing fear of clowns... and entertainer John Davidson. Depp revealed, "Clown posters, clown paintings, because clowns scare me. I have this fear of clowns, so I think that if I surround myself with them it will ward off all evil. And I have a fear of people like... John Davidson has always scared me. So I took one entire day and I watched John Davidson videotapes, him singing all these horrible songs and singing Christmas songs in polyester pants, and I watched that to overcome my fears." —XFINITY Entertainment Staff (Photo: Pascal Le Segretain/Getty Images)

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Pamela Anderson is literally afraid of her own relfection. The actress and model claims that reflective surfaces, including mirrors, give her the heebie-jeebies.

"I have this phobia: I don't like mirrors," she told the Daily Mail. "And I don't watch myself on television. If anything comes on, I make them shut it off, or I leave the room." —XFINITY Entertainment Staff (Photo by: Ethan Miller/Getty)

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Kristen Stewart revealed that she recently overcame a lifelong fear of horses in order to film "Snow White and the Huntsman." Stewart explained her equine-uneasiness at WonderCon, saying, "I broke and dislocated my elbow when I was, like, 9. I just had to not think about it. I wanted so badly to do this that it was just like, 'All right, well, if I perish by horse, that's all good.'" —XFINITY Entertainment Staff (Photo by: Pascal Le Segretain/Getty)

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"I don't like revolving doors, and I really don't like that blindspot when you're driving and go into a tunnel," he said, according to a National Ledger report. "You know that spot where you can't see for about 10 feet. You can't see what's in front of you or if someone's broken down or something in front of you." —XFINITY Entertainment Staff (AP Photo/Maja Hitij)

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Christina Ricci has admitted she is afraid of swimming pools and sharks. "I won't swim in a pool by myself because I think that somehow a little magic door is going to open up and let the shark out," she told The Insider.

The "Smurfs 2" actress is also reportedly creeped out by house plants. —XFINITY Entertainment Staff (AP Photo/Evan Agostini)

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We bet Victoria Beckham has the neatest home in all of Hollywood thanks to hubby David's fear of untidiness and disorder. "Everything has to match in the house," Victoria told People magazine. "If there are three cans of Diet Coke, he'd throw one away rather than having three because it's uneven." —XFINITY Entertainment Staff (AP Photo/Richard Drew)

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Oprah Winfrey may be one of the most powerful women in the world, but that doesn't mean she is immune to everything. In a video interview for O Magazine, Winfrey admitted her biggest fear: balloons!

"A lot of people don't know this, but I really don't like balloons," she said. "I don't like them because it reminds me of gunfire, and perhaps somewhere in my life, or past childhood, I must have had something to do with gunfire. It just really freaks me out being around balloons." —XFINITY Entertainment Staff (Photo by: Michelly Rall/Getty)

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Orlando Bloom clearly isn't afraid of pirates or supermodels, but he is absolutely terrified of pigs. The phobia was reportedly discovered when he fled from a menacing oinker on the set of "Kingdom of Heaven. —XFINITY Entertainment Staff (AP Photo/Joel Ryan)

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Getting buried alive for a scene in "Kill Bill" was a real nightmare for Uma Thurman. The blonde bombshell says she has a paralyzing fear of closed-in spaces.

"There was no acting required, real screams available," Thurman told iVillage. "It was horrific. You don't want to have that experience. Coming through the soil was also horrific." —XFINITY Entertainment Staff (AP Photo/Dan Steinberg)

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He sings... he dances... he's a huge wimp? Timberlake won't be bringing the sexy back anytime soon if a snake, spider or shark is around. The singer has admitted he is super scared of all three.

"I'm really, really scared of spiders," Timberlake told Smash Hits magazine. "I was staying at a nice hotel and I had to call reception because I spotted one in my room." —XFINITY Entertainment Staff (AP Photo/Matt Sayles)

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